With a view to defining the technical sector in which it might be applied within the overall field of rail transport, it would first be advisable to briefly look at traditional guidance systems.
A guidance system most widely used since the onset of the railway, and the most widespread universally, is the so-called “flanged wheel”, characterised by the fact that the supporting wheels—drive wheels or otherwise—perform a dual function: vehicle support and guidance.
The trunco-conical wheel has a three centimeter flange that runs along a guide rail and prevents derailing from occurring. This is, and has traditionally been, the most widely used system in railways across the world, regardless of gauge.
Another group of guidance systems is characterised by the supporting wheels being separated or disassociated from the guidance function. Support and guidance are carried out by way of independent mechanisms. In this group the different systems may be classified in two classes:                a) Lateral guidance systems, in which guidance is achieved by means of lateral bands or guides located on either side of the train. These bands or rails, located parallel and external to the wheels, imply a complicated and excessively visible installation.        b) Central guidance systems, in which guidance is achieved by means of one or two guides located beneath the centre of the train and at different heights with respect to the theoretical or actual axis of the wheels.        
The central guidance system constituting the invention for which the patent is sought is to be included under this second group b), in order to define the sector in which study is to be undertaken for the mandatory “Technical status report”.
A comparative study of the systems currently in operation allows us to state that current central guidance mechanisms might be improved upon through the application of significant innovations, and it is with this objective that we present the “CENTRAL GUIDANCE ROLLING BOX”, which aims to overcome the technical problem dealt with above by disassociating the functions of support and guidance that were previously linked in the flanged wheel, and that required the installation of a dual guidance mechanism acting independently on either side, with the disadvantages that this meant and that were underlined in describing the systems in the previous section.
Orienting the vehicle box and guidance of the wheels simultaneously implied serious difficulties that have been efficiently resolved in this case by integrating the guide mechanisms for both sides in a single solid unit, which is described below.